The present invention relates to a recoil starter for an internal combustion engine and, in particular, to a recoil starter that allows fluctuations in the pulling force of a recoil rope to be reduced.
The recoil starters conventionally used for small internal combustion engines usually have a rope reel that is rotated by pulling a recoil rope that is wound onto the rope reel and fitted with a handle. The resulting rotation of the rope reel is transmitted by, for example, a centrifugal ratchet mechanism, to the crankshaft of the internal combustion engine, thereby xe2x80x9cstart-upxe2x80x9d the internal combustion engine.
In the case of an internal combustion engine which is provided with such a recoil starter, a decompressor is frequently attached to the internal combustion engine in order to minimize the pulling force (rope pulling force) of the recoil rope that is required for starting the internal combustion engine.
It is required, in the case of the conventional recoil starter described above, to strongly and quickly pull the recoil rope in order to start up the internal combustion engine. Furthermore, although it is possible to rotate the crankshaft by pulling the recoil rope, it has been impossible to obtain a smooth rope-pulling operation due to large fluctuations of the load imposed on the recoil rope by the engine, i.e., the fluctuations originating from the compression stroke or sliding resistance of the piston relative to the rotation of the crankshaft, thereby making it difficult for a person having a weak physical strength to start the internal combustion engine.
When a decompressor is attached to the internal combustion engine, it is possible to reduce the rope pulling force required for actuating the internal combustion engine. However, the provision of a decompressor leads not only to an increased complication of the structure of the device, and hence to an increase in manufacturing cost, but also to the release of unburned air-fuel mixture into the atmosphere and contamination of the environment.
The present invention has been made to overcome the aforementioned problems. It is, in particular, an object of the present invention to provide a recoil starter that permits fluctuations of the rope pulling force to be reduced, thereby making it possible to perform a smooth rope-pulling operation and also to easily actuate the internal combustion engine, even by a person having a weak physical strength.
With a view to attaining the aforementioned object, there is provided, in accordance with the present invention, a recoil starter having a rotary driving member that is adapted to be rotated by pulling a recoil rope and an interlocking rotary member that is adapted to be rotated independently of the rotary driving member. A buffering spring is coupled between the rotary driving member and the interlocking rotary member. The buffering spring, which may be a torsion coil spring or a spiral spring, applies a rotational bias between the rotary driving member and the interlocking rotary member and is adapted to transmit the rotation of the rotary driving member to the interlocking rotary member.
In a preferred embodiment of the recoil starter according to the present invention, the rotary driving member and the interlocking rotary member are disposed on a common rotational axis.
The rotary driving member is, preferably, a rope reel which is adapted to have the recoil rope wound thereon. The rope reel may have an annular cavity, in which case the buffering member is disposed inside the annular cavity of the rope reel.
In preferred embodiments, the interlocking rotary member is a power transmission pulley to which the rotation of the rotary driving member is transmitted through the buffering member. The recoil starter further includes a centrifugal ratchet mechanism coupled to the power transmission pulley and adapted to be coupled to a crankshaft of an internal combustion engine for transmitting the rotation of the power transmission pulley to the crankshaft of the internal combustion engine.
In preferred embodiments of the recoil starter of the present invention as constructed above, when the recoil rope (recoil handle) is pulled, the rope reel of the rotary driving member is caused to rotate, and the rotation of the rotary driving member is transmitted via the buffering member to the power transmission pulley of the interlocking rotary member. The rotation of the power transmission pulley is then transmitted via the centrifugal ratchet mechanism to the crankshaft of the internal combustion engine, thereby starting the internal combustion engine through the rotation of the crankshaft.
Since the buffering member is elastically compressed in the rotational direction of the rope reel when the recoil rope is pulled, the buffering member functions not only as a power transmitting member for transmitting the rotation of the rope reel to the power transmission pulley but also as a power reservoir and a cushion or a shock absorber, thereby making it possible to minimize the fluctuations of the rope pulling force as much as possible.
Therefore, it is now possible with the recoil starter of the present invention to attain a smoother rope-pulling operation as compared with the conventional recoil starter, thereby making it possible to easily actuate the internal combustion engine, even for a person having a weak physical strength.
Furthermore, since the recoil starter according to the present invention can be constructed by simply disposing a buffering member such as a torsion coil spring in a cavity of the rope reel of a conventional recoil starter, the increases in total weight and in the manufacturing cost can be minimized. It may also not be necessary to provide a decompressor.